Two surgical lubricants were demonstrated to have a spermicidal effect in vitro on human spermatozoa obtained from the male partners of infertile couples. After incubation with either KY or Surgilube for 15 minutes, no motile or viable sperm were present in 80 per cent of the semen specimens, and less than 5 per cent of the spermatozoa were either motile or viable in the remaining 20 per cent of the semen specimens. After 30 minutes of incubation with either lubricant, no motile or viable spermatozoa could be demonstrated. Veterinary studies have shown that Lubafax has a spermicidal effect in cattle. The findings suggest that these products should not be used for vaginal lubrication by the infertile couple.